[Tutor] Why can't I make this function work? (original) (raw)
Christian Wyglendowski Christian.Wyglendowski at greenville.edu
Thu Jul 15 22:26:51 CEST 2004
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-----Original Message-----
I have written the following function as part of my guessing game program (as discussed in another thread): def Getint(): "Function to collect an integer from the user" typecheck = 0 while typecheck == 0: int = rawinput()
Something to avoid - "int" is a built-in function and type in Python. By assigning a value to "int" in your funtion, you have overwritten the built-in in your function's namespace. Thus, calls to int() from within your function will not behave as expected. Which leads us to the next issue...
if type(int) != type(1): print "Invalid input" else: typecheck = 1 return int
Raw_input() always returns a string. To get the integer value of a string, you need to call int() on it - which would present a problem in your current function with a variable named "int". After you get your variable name situation squared away, you'll find that calling int() on something that can't be converted to an integer raises an exception:
myval = 'this' int(myval) Traceback (most recent call last): File "", line 1, in ? ValueError: invalid literal for int(): this
You'll need to implement some exception handling in your function to deal with this. Perhaps this example from the interactive interpreter will get you moving in the right direction:
try: int(myval) ... except ValueError: print 'Not an integer' ... Not an integer
I think the function should keep taking input until an integer is input, at which point it should return the value to the main program. The function does not cause the program to crash but it doesn't accept any input (returns "Invalid input" whatever I type). Changing the typecheck variable should cause the while loop to exit, shouldn't it?
The loop logic of your function looks good. You just weren't reaching the case that would end the loop.
Exceptions...namespaces...weren't you just asking how to fix a simple function? :-)
For more on exceptions, see http://docs.python.org/tut/node10.html#SECTION0010200000000000000000
If you are curious about namespaces, check out the tutor archives (you can put this search string into google "namespace tutor site:mail.python.org").
Thanks for all the help, Matt.
I hope it is helpful!
Christian http://www.dowski.com
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